This invention relates to improvements in and relating to tie tampers of hand-held type used for tamping and compacting ballast gravel laid underneath ties (or sleepers) of railroad tracks.
In a tie tamper of a type known heretofore, a vibration motor (hereinafter referred to as a "vibromotor") for generating vibration as output and a handle to be grasped by an operator are connected by a leaf spring having a curve substantially of the shape of the letter S and a support leaf spring of arcuate shape. It is intended that the vibration of the vibromotor be absorbed by these leaf springs--principally by the S-shaped spring--thereby to prevent vibration from being transmitted to the handle.
In the case of a leaf spring, however, if the spring constant is made low in order to obtain a good vibration reducing characteristic, the handling characteristic of the tie tamper at the time of tamping work will become markedly poor. For this reason, it has not been possible to use springs of very low spring constants. More specifically, if an excessively weak leaf spring is used, it will be difficult for manipulative forces applied to the handle by the operator to be transmitted to the beater, which is a vibrating blade rigidly fixed to the motor, when the beater is being positioned in a specific position or when, with the beater in a state where it has been thrust into ballast gravel, it is tilted, whereby the manipulative operability of the tie tamper will become poor. For this reason, it has heretofore been necessary to use leaf springs of a certain degree of stiffness, sacrificing some of the vibration reducing characteristics of the springs. Consequently, the operators of these known tie tampers have suffered considerable fatigue.
Accordingly, the use in tie tampers of so-called Neidhart springs or dampers which have nonlinear spring characteristics, and which not only can be made to have considerably low spring constants but have various advantageous features such as high internal friction affording excellent damping characteristics is being considered.
One specific tie tamper in concrete form which reduces this concept to practice and is being considered has a handle connected to a vibromotor, to which a beater is rigidly fixed, by a combination of Neidhart dampers fixed to the handle, a shackle-like link pair fixed at one end to the square shaft of the damper, and an arcuate leaf spring pin-connected at its one end to the link pair and at its other end to the motor and by a two-bar linkage connected at its two ends via Neidhard dampers respectively to an intermediate part of the handle and to the motor, and a balance weight is provided at the pin joint between the two links of the two-bar linkage. This construction greatly reduces the vibration transmitted from the motor to the handle.
In this case, however, if the spring constants of the Neidhart dampers are so selected that when the handle of this tie tamper is grasped by the operator and pushed downward to insert the beater into ballast gravel below a railroad tie, the force applied by the operator to the handle will be transmitted well to the beater, and the vibration will also be absorbed satisfactorily, the spring constants in the reverse direction, that is, the spring constants of the dampers when the handle is pulled upward to extract the beater out from the ballast gravel underneath the tie, will become excessively small. For this reason, when the operator, holding the handle, extracts the beater out from the ballast gravel or shifts the position of the tie tamper, the link mechanism will tend to be stretched excessively, and the manipulative workability will become poor.